Hydraulic rotary rock bit



K. H. SWART HYDRAULIC ROTARY ROCK BIT Dec. 8, 1953 2 Sheets-Sheet 2 l Filed Dec. 4, 1950 ,eem/57H H. Swfzer,

INVENTOR.

ga/a! M Patented Dec. 8, 1953 UNITED STATES PATENT OFFICE HYDRAULIC ROTARY. ROCK BIT Kenneth H. Swart, Whittier, Calif., assigner to `Security Engineering Division, Whittier, Calif., a corporation of California Application December 4, 1950, Serial No. 199,054

( Cl. Z55-302) 3 Claims.

This invention relates to improvements in roller type rotary rook bits, and particularly to that type of rotary rock bit commonly referred to as the cross-section type.

Heretofore roller rotary rock bits of the crosssection type have been constructed with two opposed rotary cutters commonly referred to as the gauge cutters, and two opposed inner cutters commonly referred to as the cross cutters or the cross-section cutters. Between the four cutters constituting this group there has been usually a bridge which cooperates with the body of the bit and particularly the arms thereof in rotatably supporting' the cutters under the extremely heavy loads to which they are subjected in the course of drilling. In rotary rock bits of this character circulation ports have been provided in the body of the bit arranged to discharge the circulation fluid upon or adjacent the upper surfaces of the roller cutters on the theory that this particular location and the direction of the discharging stream of circulation fluid is necessary in order that the spaces between the cutter teeth can be properly cleaned. I have found that superior results can be obtained in a rock bit of this character by discharging either all or the major portion of the circulation fluid downwardly in an axial direction at the center of the bit so that the fluid discharged will be caused to impinge upon the bottom of the well bore and spread n therefrom over the bottom of the well bore and across the bottoms of the roller cutters. In this way, the circulation fluid not only flushes the bottom of the well bore clean of cuttings, but will also clean the spaces between the cutter teeth on the individual rollers.

It is, therefore, a primary object of the invention to provide an improved roller rock bit of the cross-section type wherein there is a circulation port through which all or at least the major portion of the circulation fluid is discharged downwardly through the bridge that is arranged between the cutters of the bit.

Another object of the invention is to provide aV 2 bit embodying the present invention,parts being broken away and shown in vertical section on a plane extending between the gauge cutters of the bit;

Fig. 2, is a bottom plane View of the bit shown in Fig. 1; and

Fig, 3 is a sectional view taken substantially upon the line 3 3 upon Fig. 1 in the direction indicated.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, the body of the improved bit may be constructed in any conventional or preferred manner, the body being generally indicated at it and having a threaded pin I i for its attachment to a drill collar on a rotary drill stem. In the bit iliustrated, there are opposed gauge cutters i2 and i3 and opposed inner or cross-section cutters iii and l5. All of these cutters are rotatably mounted against the inner sides of legs on the body of the bit and in the usual construction there is a bridge iE disposed between the cutters extending in a longitudinal direction between the gauge cutters I2 and I3. The particular manner in which the ends of the bridge are connected to or are mounted upon the body of the bit is immaterial insofar as the present invention is concerned, and consequently,

the bridge the aperture I1 is liared out toward the gauge cutters I2 and I t as indicated at 20 and a web ZI extends across this flared portion of the aperture. This web has its ends 22 and 23 offset with relation to each other and shaped to provide two cutters of a drag bit separated from each other by a vertical slot 2i. One of the blades extends to the axis of the bit but the other blade may terminate a short distance therefrom as illustrated in Fig. 2.

A feature of the invention concerm the relationship of the cutting edges of the blades with relation to the roots of the teeth of the crosssection cutters I4 and I5. The cutting edges of these blades that form a small drag bit at the bottom of the aperture I'I are preferably hori- 3 l zontally even with the roots of the teeth on the cross-section cutters. While this relationship may vary somewhat it should be maintained as close as is reasonably practical. If the cutting edges of the blades of the drag bit are located more than a reasonable amount below the roots of the teeth on the cross-section cutters I4 and l5 at the bottoms ofv these cutters, the` drag bit is in effect required to cut a pilot hole in the formation and excessive wear occurs at where the outer ends of the blades join with the flared ends of the aperture I7 in the bridge, IB, O n the other hand, if the cutting edges of the drag bit are located more than a reasonable` amountabove the roots of the bottom teeth on the cutters I4 and l5 a restriction in the circulation passages 25 and 2'! results and there is excessive yfluid cutting of adjacent metal surfaces.

It is not essential that all of the circulation fluid be discharged through the passage Il, and if desired, there may be some additional small ports in the bit arranged to discharge on top o the cutters or adjacent them. However, a major portion ci the circulation uid should be directed downwardly through the passage il in order to r obtain optimum drilling characteristics.

In relatively soft and sticky formations, bits made in accordance with the present invention have given outstanding performance in contrast with the conventional crosssection bit which tends to ball up and to stop drilling due to the accumulation of cuttings in and around the cutter teeth. The discharging circulation duid which impinges against the bottom of the well bore at the center thereof is diverted by the bottoni of the well bore outwardly across the bottom, thus flushing cuttings away from the bit and as 'the rluid traverses between the teeth on the inner and outer cutters, it tends to wash these teeth clean. In this manner, the bottom of the well bore is maintained relatively free or" cuttings and as the cutter teeth are kept in a clean condition the penetrating ability of the bit is not retarded,

In the usual construction, the bridge and its associated extension IB are made of a single piece of metal, and while the blades of the drag bit might be made integral therewith, the simplest method o1 construction is to make the web that provides these blades oi a separate piece and welded in place in the flared opening in the bottom of the bridge, thus in eiiect making it integral with the bridge.

From the above described construction it will be appreciated that an improved rotary rock bit is provided wherein the major portion of the circulation iiuid is discharged downwardly centrally of the bit and on impinging against the bottoni of the well bore, it is caused to flow outwardly across the bottoms of the cutters, thus ilushing cuttings away from the bottom or the well bore and keeping the teeth of the cutters relatively clean. The fact that the bottom of the aperture il is flared as at 20 facilitates the flow oi circulation fluid across the bottoms of the gauge cutters even though these cutters may be morev remotely located from the axis of the bit than` the cross-section cutters I and l5.

Various changes may be made in the details of construction without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

l. A rock bit comprising a hollow body attachable to a drill stem and having legs extending downwardly therefrom, toothed roller cutters rotatably mounted against the inner sides oi the legs, a bridge between the cutters having a vertically extending central aperture therethrough, a tubular extension on the bridge forming a con tinuation of said aperture leading up to the interior of the body so as to conduct circulation huid therefrom downwardly through the bridge, and drag bit cutters extending inwardly from the sides or" the aperture having their lower edges terminating approximately horizontally even with` the roots of the teeth on the roller cutters.

2. A rock bit of the cross-section type comprising a hollow body attachable to a drill stern, legs extending downwardly from the body, gauge cutters rotatably mounted against the inner sides of two opposed legs, cross-section cutters rotatably mounted against the inner sides of two other legs, a bridge extending from gauge cutter to gauge cutter and disposed between the inner ends of the cross-section cutters, means providing a passage for the discharge o1 circulation iiuid eztending from the interior of the body downwardly through the bridge, and drag bit cutters extend ing inwardly from the sides of the passage adja cent the lower end thereoiF the bottom edges ci the drag bit cutters terminating approximately even with the roots oi" the 'teeth on the cross section cutters.

3. A rock bit of the oross-section type comprisi ing a hollow body attachable to a drill stern, legs extending downwardly from the body, gauge cutters rotatably mounted against the inner sides of two opposed legs, cross-section cutters rotatably mounted against the inner sides of two other legs, a bridge extending frein gauge cutter to gauge cutter and disposed between the inner ends of the cross-section cutters, means providing a passage for the discharge of circulation duid extending from the interior of the body downwardly through the bridge, the bottom of the passage flaring laterally toward the Gauge cutters, and drag bit cutters extending inwardly from the laterally iiared portion of the passage.

KENNETH H. SWART,

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,850,358 Scott l-i/iar. 22, i932 1,992,992 Collins Mar. 5, 1935 2,047,110 Reed July 7, i936 2,058,750 Williams et al Oct. 27, 1936 2,063,327 l-owardv et al. Jan. 19, 1937 2,135,024 Barrett et al Nov. l, i938 2,244,537 Kammerer June 3, 1941 2,320,136 Kammerer May 25, i943 2,320,137 Kammerer May 25, 1943 

